The location and mounting of electrical boxes in floors has always posed a difficult problem due to the greatly varying thickness of flooring materials and flooring construction into which the floor mounted electrical box is to be installed. Such installations generally require the inventorying of a variety of electrical boxes of varying depth or the use of such electrical boxes that include the ability to shorten the depth of the box on site. The latter solution results in the necessity of having two piece electrical boxes that include a separate rear member for closing the electrical box once the proper depth has been determined.